The present invention relates generally to particle accelerators. More particularly, embodiments of the present invention relate to the reduction of dark current in particle accelerators.
Particle accelerators have been used for a number of years in various applications. For example, one common and important application is their use in medical radiation therapy devices. In this application, an electron gun is coupled to an input cavity of a linear accelerator. The electron gun provides a source of charged particles to the accelerator. The accelerator then accelerates the charged particles to produce an accelerated output beam of a desired energy for use in medical radiation therapy.
It is important to ensure that the beam output from a particle accelerator is generated efficiently and is of the desired energy. The energy and other characteristics of the beam are dependent upon the resonant frequency of the accelerator which in turn depends upon the shape and manufacture of the accelerator. The output characteristics of accelerators can be impaired as a result of the emission of unwanted electrons from the walls of the accelerator structure during operation. These unwanted electrons can be captured and accelerated by the accelerating fields in the device, resulting in the creation of so-called xe2x80x9cdark currentxe2x80x9d.
Dark current can impair the operating efficiency of a particle accelerator such as a linear accelerator. It would be desirable to provide an accelerator structure which can reduce dark current. It would further be desirable to provide an accelerator structure which can reduce dark current and which can be readily manufactured with few design changes to existing accelerator designs.
To alleviate the problems inherent in the prior art, embodiments of the present invention provide a method, system and apparatus providing reduced dark current in linear accelerators. According to some embodiments of the present invention, a method, system, and apparatus for providing reduced dark current in a linear accelerator includes a cavity having an input aperture and an output aperture, and a particle source coupled to the input aperture, the input aperture having a radius greater than a radius of the output aperture.
In some embodiments, the input aperture and the output aperture are substantially circular in shape. In some embodiments, the accelerator further includes an anode plate, coupled between the particle source and the input aperture, where the anode plate has an anode aperture and a thickness. In some embodiments, the size of the anode aperture and a thickness of the anode plate are sized to attain a resonant frequency of the linear accelerator. In some embodiments, the radius of the input aperture is selected to reduce the dark current beam generated from the anode plate.
According to some embodiments of the present invention, a cavity for a linear accelerator includes an input aperture having a first radius, and an output aperture having a second radius smaller than the first radius, where the input cavity receives particles from a particle source, and directs the particles to the output aperture.
The present invention is not limited to the disclosed embodiments, however, as those skilled in the art can readily adapt the teachings of the present invention to create other embodiments and applications.